Process for the extraction of butyric acid and its homologues



Patented Sept. 4, 1928.

UNITED STATES PATENT ()FFICE.

JACQUES LEFRANC, 0F, PARIS, FRANCE, ASSIGNOR T0 SOCIETE DES BREVETSETHAN- GERS LEFRANC & CIE, 0F PARIS, FRANCE.

PROCESS FOR THE EXTRACTION 0F BUTYRIC ACID AND ITS HOMOLOGUES.

No Drawing. Application filed January 25. 1927, Serial No. 163,571, andin France August 27,1926.

The invention relates to a process for the extraction of butyric acidfrom calcium butyrate, and more generally of the aliphatic acids fromtheir alkali and alkali-earth salts, and has for its object to provide aprocess which will provide for a ready, simple, cilicient and economicalextraction of the acid, at a commercial concentration or even at agreater concentration, although dispensing with the usual expensive.COIICQDlLIELtlOH step.

The present process is based upon the 1nsolubility of aliphatic acids ingeneral and butyric acid in particular in a solution of alkali or alkaliearth chlorides and chiefly calcium chloride; due to this insolublhtythe major part and, in some cases, almost the The calcium-chloride thusformed dissolves in the water of solution of the hydrochloric acid andin the combined or hygroscopic Water of the calcium butyrate. Theconcentration of the chloride may vary according to the moisture of thesalt and the concentration of the acid, from 50 to parts of calciumchloride for 100 parts water.

It is observed that the products of the reaction if allowed to standwill separate into two very distinct layers.

The upper layer, WhlCh may be read ly decanted or withdrawn, containsabout 75 to 100% (according to the concentration of the calcium chloridesolution) of the aliphatlc acids disengaged, at a concentration of -90per cent. 1

The lower layer, which has a greater density, is composed of the calciumchloride solution at a more or lessconcentrated state according to theamount of water contained in the hydrochloric acid and aliphatic salt.The chloride solution retains about 25 per cent of the acids, andchiefly acetic acid.

In ractice, the operation may be per forme as follows:

Hydrochloric acid and the aliphatlc salt are introduced into a suitablevessel or tank which is provided with a mechanical mixing or stirringdevice. The exact proportion is determined by calculation but thealiphatic salt should somewhat exceed the theoretical amount in order tosecure the complete saturation of the hydrochloric acid. The acid may bepoured upon the aliphatic salt or, optionally, the salt may be pouredinto the Whole amount (generally about 75 per cent) of the aliphaticacids may be recovered at a suitable concentration. The insolubility ofaliphatic acids in alkali or alkali earth chlorides is however notcomplete but it varies according to the concentration of the chloridesolution, the temperature, and other factors. Obviously, the propermeasures will be taken in order that the insolubility shall be amaximum.

If commercial hydrochloric acid is caused to react upon industrialcalcium butyrate obtained for instance by the fermentation process, thebutyrate being in slight excess, the reaction may be represented by theformula:

acids at 8590 per cent in a greater or less proportion depending uponthe concentration of the calcium chloride solution, for in stance 75 to100 per cent of the. total amount of aliphatic acids for a 30 per centcalcium chloride solution.

The lower layer consists of a calcium chloride solution which contains asmall propor tion of acids, for instance 25 per cent thereof for a 30per cent calcium chloride solution, these acids chiefly comprisingacetic acid.

The concentrated acids are collected by decanting, centrifugation orwithdrawal, and are decolored by animal black, and are. thenconcentrated upon the usual dehydrating substances such as anhydroussulphate of alumina or melted calcium chloride, and the said acids maythen be rectified by the known methods, thus oflering products havingthe maximum concentration.

The acids which are retained by the calcium chloride solution, may bereadily removed therefrom, since the material to be L liquid interposedwithin crystals). The

solution of chloride having a boiling point of some 115-130 degrees (3.,use may be made of the method of extraction by superheated steam, forexample.

This will afford a dilute solution of butyric acid which may, ifdesired, be mixed with the concentrated acids resulting from thedecantation or the withdrawal of the upper layer, either crude orrectified, so as to bring the said acids to the suitable. concentrationfor commercial purposes, such as 50, 60 or 7 0 per cent.

By way of example: 280 parts of hydrated and moist calcium butyrateobtained by the fermentation process are treated with 235 parts ofordinary hydrochloric acid; 140 parts of crude acid at 80-90 per centare obtained; by the treatment of the chloride solution 14.5 parts moreof acid are recovered; the total amount of crude acid is thus 154.5parts for 280 parts of industrial calcium butyrate.

The dissolved hydrochloric acid will not combine with the aliphaticacids; but chlorine, and especially chlorine under the action of light,may decompose the aliphatic acids.

To obviate the action of chlorine which may be due to the presence ofchlorine in the free state in the commercial acid, chlorine must beeliminated. This may be readily efl'ected due to the great afiinity ofchlorine for hydrogen, and chiefly for nascent hydrogen. To eliminatethe chlorine, it is thus suflicient to produce within the hydrochloricacid (and obviously before mixing it with the butyrate) a disengagementof nascent hydrogen for instance by the addition of a suitable amount ofiron, zinc or other metaL' In these conditions, and since theoperationis performed in the presence of an excess of an aliphatic saltwhich will quite saturate the whole of the hydrochloric acid in use,only the desired reaction will take place. i

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A process of extraction of aliphatic acids from their alkali andalkali-earth salts which consists in treating said salts withhydrochloric acid, the aliphatic salt being in slight excess, infiltering the resulting liquid whereby the excess of aliphatic salt isrecovered and in separating the lower layer formed by the solution ofchloride produced, from the major part of the insoluble aliphatic acidsforming the upper layer.

2. A process of extraction of aliphatic acids from their alkali andalkali-earth salts which consists in treating said salts withhydrochloric acid, the aliphatic salt being in slight excess, inseparating the lower layer formed by the solution of chloride produced,from the major part of the insoluble aliphatic acids forming the upperlayer and in decoloring by animal black, concentrating with adehydrating agent and rectifying the insoluble aliphatic acids.

3. A process of extraction of aliphatic acids from their alkali andalkali-earth salts which consists in treating said salts withhydrochloric acid, the aliphatic salt being in slight excess, inseparating the lower layer formed by the solution of chloride produced,from the major part of the insoluble aliphatic acids'forming the upperlayer, and In treating the solution of chloride with steam whereby thesmall amount of aliphatic acids retained therein is recovered.

4. A process of extraction of aliphatic acids from theiralkali andalka1iearth salts which consists in treatin said salts with hydrochloricacid, the alip atic salt being in slight excess, in separating'the lowerlayer formed by the solution of chloride produced, from the major partof the insoluble aliphatic acids forming the upper, layer, in treatingthe solution of chloride with steam whereby the small amount ofaliphatic acids retained therein is recovered and in mixing in suitableproportion the aliphatic acids thus recovered with the aliphatic acidsformerly separated.

5. A process ofextraction of butyric acid from calcium butyrate whichconsists in treating 280 parts of hydrated and moist calcium butyrateproduced by fermentation with 235 parts of hydrochloric acid of commerceand in separating by decantation the solution of calcium chloride fromthe insoluble butyric acid.

6. A process as claimed in claim 4 which further consists in causing thedisengagement of nascent hydrogen within the hydrochloric' acid beforeadding the same to the aliphatic salt to be treated.

In testimony whereof I have signed my name to this specification.

JACQUES LEFRANC.

